Among all the tagging applications that have I tried (i.e., Leap, iDocument, HoudahSpot, Punakea, and Tags), I prefer Tags the most.
Unfortunately, after three emails requesting support over the last month, I have yet to receive a single (even boilerplate) response from Caseapps. Since this application hasn't been updated since August, I'm left to wonder whether this application is still being supported at all. The lack of response I've received has also been the only reason I've held off on purchasing Tags.
With me, Tags has encountered problems when I have asked it to delete and rename tags (e.g. the file shows that the tag has been removed from it yet the file still appears under that tag category, etc.) and Tag Window has a scrolling bug that forces me to repeatedly resize the Tag Window as opposed to much more simply use the scrolling feature on my trackpad to go the the appropriate tag(s). There is also much room for new features, especially a Smart Folder in which I can define which tags are included (including non-overlapping tags) to accommodate special research projects.
On the note of non-response from developers, I am a license holder of Punakea, and they have never responded to any support emails, either, over a much longer period of time. So, while Punakea is by far the most similar to Tags in terms of feature set and UI, its developers are no more responsive to customer issues.
Finally, Path Finder 6, which has been talked about for two years now but has not appeared, is supposed to feature tagging. I am hoping this is released soon and that the tagging function is well-integrated into the finder.